feat(docs): union ibc spec

Author: hussein-aitlahcen

docs/astro.config.ts

@@ -155,6 +155,12 @@ export default defineConfig({
                   label: "Overview",
                   link: "/protocol/overview"
                 },
+                {
+                  label: "Specifications",
+                  autogenerate: {
+                    directory: "/protocol/specifications"
+                  }
+                },
                 {
                   label: "Channels",
                   autogenerate: {

docs/src/content/docs/protocol/specifications/ibc.mdx

@@ -0,0 +1,254 @@
+---
+title: "Union IBC"
+sidebar:
+  badge:
+    text: live
+    variant: note
+---
+
+import Mermaid from "#/components/Mermaid.astro";
+
+# Overview
+
+[`IBC`](https://ibcprotocol.org) is a blockchain interoperability protocol for secure general message passing between blockchains. At Union, we use a specialized in-house version (more EVM friendly) that slightly deviates from the _canonical_ [ibc-go](https://github.com/cosmos/ibc-go) and [ibc](https://github.com/cosmos/ibc). This document is an attempt at specifying the implementation.
+
+The semantic of the core protocol can be found in the [ibc](https://github.com/cosmos/ibc/tree/41a8caa54d8691b7fa98795d31f401e1df31e18c/spec/core) repository. Our implementation is deviating from the semantic in few places that we will describe. Most of the changes are specializations/optimizations targeting the EVM.
+
+The protocol assumes the execution happens within a smart contract engine (contract addresses **MUST** be unique).
+
+## ICS-002 Client
+
+:::note
+
+[Read more on the canonical specification](https://github.com/cosmos/ibc/tree/41a8caa54d8691b7fa98795d31f401e1df31e18c/spec/core/ics-002-client-semantics)
+
+:::
+
+- [`verifyMembership`](https://github.com/cosmos/ibc/tree/41a8caa54d8691b7fa98795d31f401e1df31e18c/spec/core/ics-002-client-semantics#state-verification) no longer takes a `delayPeriodTime` and `delayPeriodBlocks`, the specific light clients SHOULD implement such verification if necessary.
+- [`verifyNonMembership`](https://github.com/cosmos/ibc/tree/41a8caa54d8691b7fa98795d31f401e1df31e18c/spec/core/ics-002-client-semantics#state-verification)
+  - `delayPeriodTime` has been removed.
+  - `delayPeriodBlocks` has been removed.
+- [`clientIdentifier`](https://github.com/cosmos/ibc/tree/41a8caa54d8691b7fa98795d31f401e1df31e18c/spec/core/ics-002-client-semantics#identifier-validation) is a unique `uint32`. The client type **MUST** be stored and indexable with the `clientIdentifier` see.
+
+### Additions
+
+- `registerClient` **MUST** be implemented and called before being able to call `createClient` on a light client. Only one client type **MUST** exist for a given light client:
+```haskell
+registerClient ∷ ClientType → Address → IO ()
+registerClient clientType lightClient = do
+  assert (getImplementation clientType ≡ null)
+  setImplementation clientType lightClient
+```
+
+## ICS-003 Connection
+
+:::note
+
+[Read more on the canonical specification](https://github.com/cosmos/ibc/blob/41a8caa54d8691b7fa98795d31f401e1df31e18c/spec/core/ics-003-connection-semantics/README.md).
+
+:::
+
+:::caution
+
+The protocol version is considered hardcoded. We support the `Ordered` and `Unordered` features for channels only.
+
+:::
+
+- [`connectionIdentifier`](https://github.com/cosmos/ibc/tree/41a8caa54d8691b7fa98795d31f401e1df31e18c/spec/core/ics-003-connection-semantics#identifier-validation) is no longer a string but a unique `uint32`.
+- [`ConnectionEnd`](https://github.com/cosmos/ibc/tree/41a8caa54d8691b7fa98795d31f401e1df31e18c/spec/core/ics-003-connection-semantics#data-structures)
+  - `counterpartyPrefix` has been removed.
+  - `version` has been removed.
+  - `delayPeriodTime` has been removed.
+  - `delayPeriodBlocks` has been removed.
+```haskell
+type ClientIdentifier = Uint32
+type ConnectionIdentifier = Uint32
+
+class ConnectionEnd where
+  state ∷ ConnectionState
+  counterpartyConnectionIdentifier ∷ ConnectionIdentifier
+  clientIdentifier ∷ ClientIdentifier
+  counterpartyClientIdentifier ∷ ClientIdentifier
+```
+
+
+## ICS-004 Channel and Packet
+
+:::note
+
+[Read more on the canonical specification](https://github.com/cosmos/ibc/blob/41a8caa54d8691b7fa98795d31f401e1df31e18c/spec/core/ics-004-channel-and-packet-semantics/README.md)
+
+:::
+
+### Channel
+
+:::caution
+
+We do not support the [Channel Upgrade](https://github.com/cosmos/ibc/blob/41a8caa54d8691b7fa98795d31f401e1df31e18c/spec/core/ics-004-channel-and-packet-semantics/UPGRADES.md) feature.
+We only support `Ordered` and `Unordered` channels.
+
+:::
+
+- [`channelIdentifier`](https://github.com/cosmos/ibc/blob/41a8caa54d8691b7fa98795d31f401e1df31e18c/spec/core/ics-004-channel-and-packet-semantics/README.md#identifier-validation) is no longer a string but a unique `uint32`.
+- [`ChannelEnd`](https://github.com/cosmos/ibc/blob/41a8caa54d8691b7fa98795d31f401e1df31e18c/spec/core/ics-004-channel-and-packet-semantics/README.md#definitions):
+  - `connectionHops` has been renamed to `connectionId` and it's type changed from `[connectionIdentifer]` to `connectionIdentifier`.
+  - `upgradeSequence` has been removed.
+```haskell
+type ChannelIdentifier = Uint32
+data ChannelOrder = Ordered | Unordered
+data ChannelState = Init | TryOpen | Open | Closed
+
+
+class ChannelEnd where
+    state ∷ ChannelState
+    ordering ∷ ChannelOrder
+    connectionId ∷ ConnectionIdentifier
+    counterpartyChannelId ∷ ChannelIdentifier
+    counterpartyPortId ∷ String
+    version ∷ String
+```
+
+### Packet
+
+:::caution
+
+The [ICS-05 port allocation](https://github.com/cosmos/ibc/blob/41a8caa54d8691b7fa98795d31f401e1df31e18c/spec/core/ics-005-port-allocation/README.md) module has been removed, channel identifiers uniquely identify protocols and the implementor **MUST** ensure there is an existing indirection from `channelIdentifier -> protocolAddress`.
+
+:::
+
+- [`Packet`](https://github.com/cosmos/ibc/blob/41a8caa54d8691b7fa98795d31f401e1df31e18c/spec/core/ics-004-channel-and-packet-semantics/README.md#definitions)
+  - `sourcePort` has been removed.
+  - `destinationPort` has been removed.
+  - `timeoutHeight` type has been changed from `(uint64, uint64)` to `uint64`.
+```haskell
+class Packet where
+    sequence ∷ Uint64
+    sourceChannel ∷ ChannelIdentifier
+    destinationChannel ∷ ChannelIdentifier
+    payload ∷ [Uint8]
+    timeoutHeight ∷ Uint64
+    timeoutTimestamp ∷ Uint64
+```
+
+## ICS-024 Host
+
+:::note
+
+[Read more on the canonical specification](https://github.com/cosmos/ibc/blob/41a8caa54d8691b7fa98795d31f401e1df31e18c/spec/core/ics-024-host-requirements/README.md#synopsis)
+
+:::
+
+### Path-space
+
+Union approach to the path-space is deviating from the canonical implementation. Since we no longer use string for client/connection/channel identifiers, the commitment paths are binary.
+
+```haskell
+type Prefix = Uint256
+
+clientStatePrefix ∷ Prefix
+clientStatePrefix = 0x00
+
+consensusStatePrefix ∷ Prefix
+consensusStatePrefix = 0x01
+
+connectionsPrefix ∷ Prefix
+connectionsPrefix = 0x02
+
+channelsPrefix ∷ Prefix
+channelsPrefix = 0x03
+
+packetsPrefix ∷ Prefix
+packetsPrefix = 0x04
+
+packetAcksPrefix ∷ Prefix
+packetAcksPrefix = 0x05
+
+nextSeqSendPrefix ∷ Prefix
+nextSeqSendPrefix = 0x06
+
+nextSeqRecvPrefix ∷ Prefix
+nextSeqRecvPrefix = 0x07
+
+nextSeqAckPrefix ∷ Prefix
+nextSeqAckPrefix = 0x08
+
+commit ∷ AbiEncode a ⇒ a → Bytes32
+commit x = keccak256 (abiEncode x)
+
+clientStateKey ∷ ClientIdentifier → Bytes32
+clientStateKey clientId = commit (clientStatePrefix, clientId)
+
+consensusStateKey ∷ ClientIdentifier → Uint64 → Bytes32
+consensusStateKey clientId height = commit (consensusStatePrefix, clientId, height)
+
+connectionKey ∷ ConnectionIdentifier → Bytes32
+connectionKey connectionId = commit (connectionsPrefix, connectionId)
+
+channelKey ∷ ChannelIdentifier → Bytes32
+channelKey channelId = commit (channelsPrefix, channelId)
+
+packetKey ∷ ChannelIdentifier → Bytes32 → Bytes32
+packetKey channelId packetHash = commit (packetsPrefix, channelId, packetHash)
+
+packetReceiptKey ∷ ChannelIdentifier → Bytes32 → Bytes32
+packetReceiptKey channelId packetHash = commit (packetAcksPrefix, channelId, packetHash)
+
+nextSequenceSendKey ∷ ChannelIdentifier → Bytes32
+nextSequenceSendKey channelId = commit (nextSeqSendPrefix, channelId)
+
+nextSequenceRecvKey ∷ ChannelIdentifier → Bytes32
+nextSequenceRecvKey channelId = commit (nextSeqRecvPrefix, channelId)
+
+nextSequenceAckKey ∷ ChannelIdentifier → Bytes32
+nextSequenceAckKey channelId = commit (nextSeqAckPrefix, channelId)
+```
+
+
+## Extensions
+
+### ICS-004 Packet
+
+The `packetKey` and `packetReceiptKey` are special commitments that no longer takes a `sequence` but the whole packet hash. This allows us to extend the protocol with batching for sent packets and written acknowledgements.
+
+```haskell
+setCommitment ∷ Store → Bytes32 → Bytes32 → Store
+getCommitment ∷ Store → Bytes32 → Bytes32
+
+commitmentMagic ∷ Bytes32
+commitmentMagic = 0x0100000000000000000000000000000000000000000000000000000000000000
+
+mergeAck ∷ Bytes32 → Bytes32
+mergeAck ack =
+  commitmentMagic |
+    (ack & 0x00FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF)
+
+commitmentExist ∷ Store → Bytes32 → Packet → Bool
+commitmentExist store expectedCommitment packet =
+  getCommitment store (commit packet) ≡ exceptedCommitment
+
+batchSend ∷ Store → [Packet] → Store
+batchSend store packets = do
+  assert (all (commitmentExist store commitmentMagic) packets)
+  setCommitment store (packetKey channelId (commit packets)) commitmentMagic
+
+batchAcks ∷ Store → [Packet] → [Ackowledgement] → Store
+batchAcks store packets acks = do
+  assert (
+    all
+      (\(ack, packet) -> commitmentExist store (mergeAck ack) packet)
+      (zip acks packet)
+  )
+  setCommitment
+    store
+    (packetReceiptKey channelId (commit packets))
+    (mergeAck (commit acks))
+```
+
+
+:::tip
+
+The `commitmentMagic` value and `mergeAck` function are present to reuse the same slot to commit the receipt and the acknowledgement hash. This drastically lower the gas cost on EVM.
+
+Receipts are written when a packet is received. Acknowledgements when the execution of a received packet completes. Because of the asynchronous nature of the acknowledgement, we must store a receipt to avoid replay attacks.
+
+:::

evm/contracts/core/24-host/IBCCommitment.sol

@@ -36,13 +36,6 @@ library IBCCommitment {
         return abi.encode(CHANNELS, channelId);
     }
 
-    function packetCommitmentPath(
-        uint32 channelId,
-        uint64 sequence
-    ) internal pure returns (bytes memory) {
-        return abi.encode(PACKETS, channelId, sequence);
-    }
-
     function batchPacketsCommitmentPath(
         uint32 channelId,
         bytes32 batchHash
@@ -102,13 +95,6 @@ library IBCCommitment {
         return keccak256(channelPath(channelId));
     }
 
-    function packetCommitmentKey(
-        uint32 channelId,
-        uint64 sequence
-    ) internal pure returns (bytes32) {
-        return keccak256(packetCommitmentPath(channelId, sequence));
-    }
-
     function batchPacketsCommitmentKey(
         uint32 channelId,
         bytes32 batchHash